Refudiate: dupper or brunch?

From online source:

"For a portmanteu word to be worthwhile, the two words it blends should have distinct meanings. "Brunch" is a useful word because breakfast and lunch aren't the same thing. But if someone combined dinner and supper into a new word (e.g. dupper), what purpose would it serve? Granted, "refute" and "repudiate" may have subtle differences in meaning, but that doesn't seem like much of a defense. Out of all the established portmanteu words in our language, is there a single one where the two words from which it derives are anywhere close to being synonyms?"